Senior UI Developer

Function

We’re looking for a specialized Senior UI Developer to join our client’s digital product team and take full ownership of a mission-critical Component Library. Acting as the guardian of the design system, you will maintain and evolve a high-performance library built on Vanilla JavaScript and SCSS, distributed via NPM, while ensuring pixel-perfect execution, strong accessibility standards, and operational stability. You will operate at the intersection of design, engineering, and functional requirements, working autonomously while empowering a small team of developers.

Responsibilities

• Own the architecture, maintenance, and evolution of a core component library using clean, modular Vanilla JS and SCSS.

• Translate Figma designs into high-fidelity, reusable components that accurately reflect design intent and interaction patterns.

• Lead on accessibility, ensuring strict compliance with WCAG and ARIA standards across all components.

• Manage the release lifecycle of the library as an NPM package, including versioning, parallel environments, and deployment discipline.

• Ensure cross-browser and multi-device quality through rigorous testing, with particular attention to iOS Safari.

• Support integration of components into TypeScript, React, and Next.js environments in collaboration with other developers.

• Act as an L2/L3 escalation point for critical UI incidents, contributing to 24/7 production resilience when needed.

• Maintain clear documentation and templates using Nunjucks, and uphold high standards for linting, testing, and code quality.

Profile of the ideal candidate

• Minimum 7 years of professional front-end experience, including at least 5 years working with component libraries or design systems in Vanilla JavaScript (ES6+) and SCSS.

• Proven experience with server-side rendering, API integration, and integrating a headless CMS (Sitecore or equivalent).

• Expert knowledge of accessibility (WCAG 2.1+, ARIA), Figma, and modern front-end tooling, including NPM package management and SemVer.

• Hands-on experience with cloud-based cross-browser testing tools such as BrowserStack.

• Strong understanding of different rendering engines (WebKit, Blink, Gecko), mobile responsiveness, and the quirks of iOS Safari.

• Solid grounding in Agile ways of working, with a collaborative, mentoring, and solution-oriented mindset.

Practicalities and added value

• C1-level English (spoken and written) is required.

• Hybrid working model with two days per week on-site at our client’s office, including a mandatory presence on Mondays.

• Strong communication skills, with the ability to explain complex technical concepts clearly to both technical and non-technical stakeholders.